This invention pertain to a mixing system and method for batch mixing and dispensing liquids such as dampening solutions or silicone emulsions used in the printing industry. The mixing system is useful in providing the spray dampening fluid for the spraying system of co-pending application Ser. No. 518,470, filed July 29, 1983, entitled "Variable Frequency Spray Dampening System". The system is also useful in providing a silicone emulsion of the type applied to a paper web as the web is moving through a printing press such system being described in co-pending application Ser. No. 770,104, filed Aug. 28, 1985, and entitled "Apparatus and Method for Applying Silicone Emulsion to a Paper Web".
In preparing either a spray dampening solution or a silicone emulsion, quantities of the constituent liquids are charged into a mixing tank and mixed as a batch. It is highly desirable, however, to automate this process so that when the batch mixture has been discharged from the system, the system will automatically begin mixing another batch. One such mixing system for dampening solutions is disclosed in co-pending application Ser. No. 647,893, filed Sept. 6, 1984, entitled "Liquid Mixing System". This system discloses a process for continuous batch mixing in a mixing vessel and discharging into a feed tank which is constantly under pressure. Other mixing system have required complex proportional mixing devices such as liquid motor drives and metering pumps as well as loss motion pumps. Not only were such systems complex, but they required sensing devices which were usually emersed in the liquids and thus subject to corrosion, contamination and coating which would create inaccuracies in devices. Moreover, with the prior art systems, adjustments or variations in the amounts of the liquids were difficult or required complex counters or adjustable metering devices which were difficult to maintain in proper working order.